The hypothesis that the renal kallikrein-kinin system is involved in normal kidney function and control of systemic arterial pressure has been strengthened by new data. The data include: confirmed correlations among urinary kallikrein, blood pressure, race, and other parameters in normal children; more evidence of altered system activity in normal subjects during certain manuevers, as well as in hypertensive and non-hypertensive diseases; localization of system components within the kidney, and information about the regulation of their activities; additional insight into the biochemical properties of kallikrein and kinins; and advances in measurement technology. The proposed research will explore relations among the kallikrein-kinin system, aldosterone, electrolytes, and systemic blood pressure. We shall determine: if kallikrein is an aldosterone-induced protein; if maneuvers, drugs or disease which alter adrenal/renal function and/or blood pressure, affect the activity of the system and conversely, if altered system activity affects electrolyte excretion and blood pressure; if urinary kallikrein levels are continually correlated with blood pressure as normal children age and are subjected to exercise stress. Kallikrein, kinins and kininogens will be measured with radiochemical, radioimmuno-, spectrophotometric and biologic assays. Urinary prostaglandin E-like material and plasma renin activity will be measured and relations sought amongst these materials and the kallikrein-kinin system. Normal volunteers and patients with hypertensive diseases, as well as hypertensive rat models will continue to be studied. Our objectives are: 1) to continue to define factors which influence urinary kallikrein and kinin excretion; 2) to continue to describe the control and function of the renal kallikrein-kinin system; 3) to continue to assess the role of the system in hypertensive diseases; and 4) to determine whether or not kallikrein is an aldosterone-induced protein.